Manufacturers of electric power tools usually offer different battery packs of different physical sizes and rated voltages, each battery pack being allocated, in terms of its physical size, rated voltage, and/or power level, to a specific model of electric power tool. It is also usual to offer different types of battery, for example NiCd batteries, nickel/metal hydride (NiMH) batteries, and lithium-ion (Li-ion) batteries. Li-ion batteries are particularly widely used because of their high power density. The rated voltage and capacity of the particular battery packs that are used or available generally determine the power level and running time of the electric power tools.
Electric power tools that require a large amount of energy and in which very high power peaks may also be briefly necessary, for example large angle grinders or chainsaws, cannot, however, be operated efficiently using presently available battery packs. In addition, particular rules regarding transportation safety and handling exist for Li-ion batteries once a certain capacity is exceeded. The profitability of such large Li-ion battery packs is thereby disadvantageously influenced.
German Patent Application No. DE 10 2008 040 061 A1 describes an electric power tool, having a network-independent power supply, in which operation at high energy consumption with large power peaks and an extended running time is efficiently possible using presently available battery packs. The electric power tool encompasses an interface by which the electric power tool is mechanically and electrically connectable to a battery pack. Provided for this purpose is a coupling apparatus that is mechanically and electrically connectable, via the interface, to the electric power tool. The coupling apparatus has a first battery interface for connection to a first battery pack, and a second battery interface for connection to a second battery pack. The electric power tool can be operated selectably using a single battery pack, two battery packs electrically connected in parallel, or two battery packs electrically connected in series.